High-temperature fan



C. NYGREN HIGH TEMPERATURE FAN Dec. 28, 1948.

5 Sheets-Sheet 1 Filed May 19, 1945 INVENTOR. iczr/ fl/yyrefl' Dec. 28, 1948. c. NYGREN' 2,457,711

HIGH TEMPERATURE FAN Filed May 19, 1945' s Sheets -Sh eet 2 ..|.iHm1 WW Cwr'ljlf were Dec. 28, 1948. c. NYGREN HIGH TEMPERATURE'FAN 5 Sheets-Sheet -3 Fil'ed May 19,1945

fiwenio fad/we s.

Dec. 28, 1948. c. NYGREN 2,457,711

HIGH TEMPERATURE FAN Filed May-19, 1945 5 hets-Sheet 4 I Mil i Dec. 28, 1948. c. NYGREN 2,457,711

HIGH TEMPERATURE FAN Filed Ma 19, 1945 5 s heetswsheet 5 225 t 555 /?9 E Cliff 5 7224 Z? 57 fiwenfor Patented Dec. 28, 1948 UNITED STATES PATENT OFFICE 1 I 2.457.711 HIGH TEMPERATURE Carl Nygren, Michigan City, Ind; assigrnor to Michia'na Products Corporation, Michigan City, 11111., a corporation of Indiana Application May 19, 1945, Serial No. 5941150 This invention relates to centrifugal fans or blowers for heat treating furnaces and the like, and'the principal object of the invention is to provide a simple construction that can be readily manufactured from suitable heat and corrosion resisting alloys and will allow appropriate ireedom of movement among the parts in expanding and contracting while maintaining dynamic balance of the whole in use.

Generally speaking, this is accomplished by fastening a plurality of separate, like blades to hub members in circular arrangement about a common axis of rotation and making each blade bear a corresponding shroud portion. Preferably, each blade and a segment of shroud is made in one piece interengaged with adajacent segments of shrouds throughout the series. particularly advantageous in a design for small, low-cost iansfor example, of 15 inches in diameter.

Preferred embodiments of the scheme of construction are shown in the accompanying drawings, in which:

Figs. 1 and 2 are diagrammatic views of a double inlet fan and its associated parts in one form of installation;

Fig. 3 is ahalf plan view and half longitudinal section of a double inlet fan. taken along the axis of rotation showing a specifically different fan structure;

Fig. 4 is afront elevationo'f one of twelve blades used in this fan;

Fig. -5 is an end elevation of one-half of the blades shown in Fig. 4 looking from the top in that figure;

Fig. '6 is a side elevation of the blade shown in Fig. 4;

Fig. 7 is a part end elevation and part crosssection at right angles to the axis of rotation of the fan shown in .Fig. 3;

Fig. 8 is a front elevation of one of the hub members;

Fig. 9 is an axial section of the hub members shown in Fig. 81'

Fig. 10 is a half elevation and half section of a single inlet fan corresponding to the double inlet fan shown in Fig. 3;

Fig. '11 is a front elevation of one of the twelve blades used in the single inlet fan shown in Fig. 10';

Fig. 12 is a side elevation of the blade shown in Fig. 11;

Fig. 13 is an axial section of one-half of the double inlet -fan having a difierent form of shroud section carried by the blades;

This is Fig. 14 is a front elevation of one of the blades;

Fig. 215 is a side elevation of the blade shown in Fig, '14 looking from the right in that figure;

Fig. 16 is an end elevation or that blade looking from the top in "Fig. 14, the intermediate part being broken away; a a I Fig. 17 is a side elevation corresponding to Fig. 14 of a corresponding blade in a single inlet tan; and

Fig. 18 is a side elevation of the same looking from the right in Fig. 17. l

But these particular drawings and the corresponding description are used for the purpose of illustration only and are not intended to impose unnecessary limitations on the claims.

In Figs. 1 and 2, 10 indicates a conventional form of masonry installation for a fan orblowcr within which is a metal casing I l for a double inlet fan 12 mounted on a hollow-water-cuold shaft 13, .journaled in bearings l 4 and driven by a motor (I5 through a V-belt drive 16. The inlet side of the water cooling unit is shown generally at H and the outlet side is shown generally at 18.

Water cooling ordinaril used in fan as: struction. for propelling high temperature fluids such as the gases eirculated heat treating hn'naces. V

The fan shown in Figs. 3-9 (sheets 2 and 3) is composed of two hub members 3 mounted on the shaft 13 and twelve bladesllfl, each formed integral with two shroud sections 21, which together formthe shrouds generally indicated by 22.

Each shroud section 24 is really a segment of a circular ring projecting at each side of the body :of the :blade 2!! and having near the upperright corner in Fig. 6 machined faces 23 ateach side adapted to make a push joint between the flanges 2d of :a fork :25 at the opposite edge of the adjacent shroud element 2!. The flanges 24 point to the rear with respect to the direction of rotation and the :forks are appropriately streamlined so as to prevent turbulence in the gases "propelled by the fan. The machined faces 23 cooperate with machined faces 26 on the inner sidesof the flanges 24. i

This construction forms shrouds which can expand and contract in every way with perfect freedom while performing their functions in the fan, and each section of each fan is borne directly by a corresponding blade, which thus .servesto take all the stress due to centrifugal force on the shrouds and the outer portions of the blades. It remains only to secure *or fasten the inner por tions of the blades to hub portions and provide for proper driving relationship. and the fan is complete in all its important particulars. This can be done in a great variety of ways. As shown in Figs. 3-9, the inner portion 21 of each blade 20 has its corners cut away at 28 to provide inlets for the fan, and each terminates in a base portion 29 generally parti-cylindrical in shape and provided with bosses 30 having openings 3| to receive pins 32, which also enter openings 33 in the flanges 34 of the hub portions [9, and this serves to cross-fasten the inner portions of all the blades to the hub portions at a uniform distance from the axis of rotation and provide a datum line on Which the resistance to individual outward movement of the blades is established.

Outwardly from the parti-cylindrical portions 29 at each side thereof, the inner portions 21 of the blades are provided with machined faces 35 adapted to make a push joint in notches 36 in the outer peripheries of the flanges 34 of the hub portions [9, thus providing a driving relationship between the hub portions and the blades at a sufficient distance from the axis of rotation to provide great strength without concentration of stresses. In this instance, the flages 34 are 6 /2 in diameter for a wheel. A diameter of 12" would be appropriate for a 30 fan.

The left hub member 19 comes torest against a shoulder 31 on the shaft l3, the two hub members are separated by a sleeve 38, and the right hub member 19 is made fast by a threaded collar 39 locked by a nut 40 and a washer 4 l. The collar will be set up wrench tight on first assembly, and then backed off an amount corresponding to the calculated expansion or such as may be determined by test with the particular alloys, the temperature of operation, and the cooling of the shaft.

Pins 32, in diameter, fitted to corresponding sockets with tolerances of plus .001 minus .000 have been found satisfactory. Machined faces 23 and 2B, /2" radially and up .to A circumferentially, have been found satisfactory. Tolerances of plus .002" minus .003 are 'allowable. Blades having a thickness of ti at the outer end and at the machined faces 35 have been found satisfactory; and, generally speaking, the body of the blades should taper outwardly from the cylindrical bases 29 and the bosses 30 should be connected with the adjacent portion of the blades by flanges 42.

The relatively great distance of the side faces of the notches 36 and the meeting machined faces 35 on the blades from the axis of rotation makes it unnecessary to work to very close tolerances in order to have close driving connections with freedom to expand and contract.

The notches 36 in the hub flanges 34 andthe corresponding machine faces 35 on the blades are finished to give a circumferential flt within plus .002" minus .000, but the radial fit is purposely made with about clearance.

The single inlet fan shown in Figs. 10-12 (sheet 4) corresponds to the double inlet fan in all particulars except that the left side is cut away and the shroud portions l2l are extended inwardly to close that side of the fan. 0therwise, it is deemed suflicient to apply corresponding reference numerals throughout Figs; 10-12.

The construction of the inner ends of the blades and their inter-relation with the hub members may be varied greatly. Suitable variations are shown described and claimed in the copending application Ser.-No. 590,753, filed April 4 28, 1945, reference to which is intended to include the disclosure therein.

The outer portion of the blades and the shroud segments are also subject to considerable variation. Illustrations are given in Figs. 13-18 (sheet 5) in which the shroud segments 22! project for the most part from the right side of the blades 20 asviewed in Fig. 15 and have tongues 223 adapted to make a push joint with the opposite sides of grooves 224 between flanges 225 on the opposite or left edge of the blade as it appears in Fig. 15. Each of the shroud segments 22I cooperates with adjacent segments around the circular arrangement to form a complete shroud. The grooves 224 face to the rear in rotation, and the parts are appropriately streamlined to avoid turbulence.

In the preferred procedure, the shaft I3 and the nuts 39 and 40 are made of carbon steel, the remaining portions being made of suitable alloy to be selected according to the temperatures and the corrosive nature of the atmosphere in which the fan is to be used. Those skilled in the art will readily choose alloys having appropriate strength consistent with the temperatures and the corrosive nature of the atmosphere, and will realize that many alloys having desirable strength and heat resistance do not have the corrosive resistance; and many having the desirable corrosive resistance do not have as high strength or heat resistance as some of the others, and will thus make variations in design to correspond with the choice of materials.

The parts are preferably machined to make corresponding elements substantially identical, and are then heat treated to relieve any strains.

The temperature of the annealing should be above that expected in service.

After this treatment, assembly and a little out and try will effect dynamic balance, which the scheme of construction will maintain throughout a long period of service.

I claim:

1. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their inner portions converging inwardly toward said axis and their outer portions diverging outwardly from said axis, hub members at either side, means to fasten the inner portions of the blades to the hub members to hold them against individual bodily movement outwardly due to centrifugal force, means fastening the intermediate portions of the blades to the hub members against relative rotary movement in driving and segment shaped shroud sections carried by the outer portions of the blades in circular arrangement about the axis to form shrouds for the fan.

2. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their inner portions converging inwardly toward said axis and. their outer portions diverging outwardly from said axis, hub members at either side, means to fasten the inner portions of the blades to the hub members to hold them against individual bodily movement outwardly due to centrifugal force, other means to fasten the blades and hub members against relative rotary movement in driving, and segment shaped shroud sections carried by the outer portions of the blades in circular arrangement about the axis to form shrouds for the fan.

3. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their inner portions converging inwardly toward said axis and their outer portions diverging outwardly from said axis, hub members at either side, pins connecting the hub members to the inner portions of the blades to hold them against individual bodily movement outwardly due to centrifugal force, tongue and groove connections between the hub members and the blades to provide driving relationship, and segment shaped shroud sections carried by the outer portions of the blades in circular arrangement about the axis to form shrouds for the fan.

4. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their inner portions converging inwardly toward said axis and their outer portions divergin outwadly from said axis, hub members at either side, pins connectin the hub members to the inner portions of the blades to hold them against individual bodily movement outwardly due to centrifugal force, and driving connections between the hub members and the blades outwardly with respect to the pins.

5. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their inner portions converging inwardly toward said axis and their outer portions diverging outwardly from said axis, hub members grasping the blades by their inner portions to hold the blades against individual bodily movement outwardly due to centrifugal force, and segment shaped shroud elements borne by the outer portions of the blades having interfitted tongued and grooved edges cooperating to form shrouds for the fan.

6. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their inner portions converging inwardly toward said axis and their outer portions diverging outwardly from said axis, hub members at either side, means to fasten the inner portions of the blades to the hub members to hold them against individual bodily movement outwardly due to centrifugal force, other means outwardly of the first to maintain a driving connection between the hub members and the blades, and segment shaped shroud sections carried by the outer portions of the blades in circular arrangement about the axis to form shrouds for the fan.

7. In a centrifugal fan, a plurality of blades in circular arrangement about a common axis of rotation with their inner portions converging inwardly toward said axis and their outer portions diverging outwardly from said axis, hub members at either side, pins in circular arrangement about the axis connecting the hub members with the inner portions of the blades to hold them against individual bodily movement due to centrifugal force, and a tongue and groove driving connection between the hub members and the blades outwardly of the pins.

CARL NYGREN.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 629,121 Bicalky July 18, 1899 1,036,627 Huguenin Aug. 27, 1912 1,258,462 Rice Mar. 5, 1918 FOREIGN PATENTS Number Country Date 14,808 France Feb. 19, 1912 

